RE: Opisthocoelicaudia (was Re: Titanosaurids)

["Tracy L. Ford" <dino.hunter@home.com>]

-----Original Message-----
From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
Mickey_Mortimer11
Sent: Wednesday, January 23, 2002 8:19 PM
To: dinosaur@usc.edu
Subject: Re: Opisthocoelicaudia (was Re: Titanosaurids)


> Oh, yes it is. There are sauropod columns with just a few bifid vertebrae
and
> there are sauropod columns in which practically all the vertebrae are
bifid.
> Each vertebra needs to be scored individually.

Just picture all the characters in my coelurosaur study- cervical 1 without
pleurocoels...... dorsal 9 with two pleurocoels....... caudal 34 without
transverse processes.  Ahhhhh!  With all of their caudals uniquely
procoelous, alvarezsaurids would be monophyletic without doubt, supported by
a Bremer index of 25 based on caudal central morphology alone!  Obviously,
such a division of characters would represent a weighting problem.  A better
solution (which many people utilize) is to have multiple states in a single
character to represent changes along the vertebral column.<<
AH, the lazy way, Don't look at the whole skeleton. I get it. Now I know how
cladistic works :) Or ignoring partial or fragmentary individuals or
ignoring them all together. Ok, lets say they do it as you say, how do we
know what they choose is right? Or, how do we know they haven't missed an
important variation in their characters? Me, I always like the one where
they say the cladagram didn't turn out the way they wanted it to so they
Twiked it to fit :) If it don't work , make it work.


Tracy Ford wrote-

> To me, it's pretty ludicrous that there is only one group of Late
Cretaceous
> Sauropods. One thing is the cladistical analysis and they are looking at
> numbers and not the actual specimens. The Diplodocid looking titanosaurs,
> are IMHO diplodocids, the Camarasaur looking titanosaurs are IMHO
> camarasaurds, etc. There is new evidence, still being worked on, that
> will...Ok, I won't be mean...

We also have rebbachisaurids (Calvo and Salgado, 1995; Novas, 1997; Lamanna
et al., 2001; Antarctosaurus in part?) and brachiosaurids (Kirkland et al.,
2000; Rauhut and Werner, 1997), not to mention questionable dicreaosaurids
(Russell et al., 1994) and diplodocids (McIntosh et al., 1992).  Plus, the
titanosaur group containing Late Cretaceous members (including Austrosaurus,
Huabeisaurus and titanosauroids proper) is a pretty big part of the sauropod
tree.  Upchurch's cladistic analyses on sauropods all use genera for OTU's,
so a priori combining Late Cretaceous taxa into a single family is not a
question.  New evidece is always interesting though....

Mickey Mortimer<<
You did read what I wrote right? I wrote Late Cretaceous. Rebbachisaurids
are Early Cretaceous. You probably don't know this but the brachiosaur that
Kirkland et al talk about is actually a large hadrosaur. He was rather upset
about that at the SVP in Mexico City :(. Right about Rauhut et al. Check my
list for other Late Cretaceous sauropods, and found some more diplodocids.
But they do lump late Cretaceous sauropods into titanosaurs as I previously
mention.